Its interesting that they put them on a ruler, but dont measure the bolt properly (underhead length) or in the correct unit. I suppose it helps sell...
It is very common to remove the rear of the frame as you describe, Many PRV cars have this modification. You do not need to angle the engine so much...
The nuts are independent of one another. If the rear nut is not tight the taper does not properly engage. Since you cannot get a torque wrench on it,...
That's strange, I did not recall asking your opinion. You are not familiar with this situation so I do not see how you feel qualified to evaluate it...
I linked this thread to you for reading, Not to try and convince Nick to sell you an input shaft. He has said more than once he is not selling them,...